Showing papers on "Cyclopropane published in 1993"
TL;DR: In this article, the synthesis of five carbocyclic dideoxynucleosides with a bicyclo[3.1.0]hexane skeleton was accomplished via a Mitsunobu-type coupling reaction with various heter-cyclic bases.
78 citations
TL;DR: In this article, the protonated cyclopropane mechanism was used to explain the observed sharp increase in reaction rate with increasing carbon number of normal paraffins above C[sub 7] in catalytic cracking.
Abstract: Experimental results obtained in studies on catalytic cracking of normal paraffins as described in the literature are interpreted in terms of the protonated cyclopropane mechanism described in the previous paper of this series. It is shown that this mechanism is capable of explaining the observed sharp increase in reaction rate with increasing carbon number of normal paraffins above C[sub 7] in catalytic cracking. It also provides an explanation for many characteristic features of the product spectra, such as the virtual absence of C[sub 1] and C[sub 2] as primary cracking products, the high degree of branching in the saturated fractions in contrast to the predominantly linear structures in the light olefin fractions, and the relatively low formation of C[sub 3] as compared with C[sub 4] and higher homologs under conditions where secondary cracking is minimized.
59 citations
TL;DR: Alkylidene cyclopropane derivatives are obtained by reaction of biscyclopropyl titanocene with several types of carbonyl compounds, including aldehydes, ketones and esters.
57 citations
TL;DR: In this paper, a cyclopropane structure of C60(CCl2) was determined by 13C NMR spectroscopy at the 6-ring/6-ring junction.
54 citations
TL;DR: In this paper, the X-ray structure of the binuclear complex tetrakis[(4S)-4-phenyloxazolidin-2-one]-dirhodium(II) ([Rh2{( 4S)-phox}4]) is reported.
Abstract: The synthesis and X-ray structure of the binuclear complex tetrakis[(4S)-4-phenyloxazolidin-2-one]-dirhodium(II) ([Rh2{(4S)-phox}4]) are reported. Structure-selectivity comparisons are made for typical metal carbene transformations, such as inter- and intramolecular cyclopropane formation, intermolecular cyclopropene formation and intramolecular C–H insertions of diazoacetates and diazoacetamides. The enantioselectivity achieved in the [Rh2{(4S)-phox}4]-catalyzed reactions is intermediate between that of [Rh2{(5S)-mepy}4] and [Rh2{(4R)-bnox}4], which were described previously (mepy = methyl 5-oxopyrrolidine-2-carboxylate; bnox = 4-benzyloxazolidin-2-one). In contrast to other catalyzed intermolecular cyclopropane formations, those using [Rh2{(4S)-phox}4] result preferentially in formation of the cis-cyclopropane.
53 citations
TL;DR: In this paper, the gas-phase reactivity of bare neutral transition metal atoms with alkanes and alkenes has been studied in the 4D series. But the results of the 4d series were limited to the ground state of the Pd atom.
Abstract: The authors and others are surveying the gas-phase reactivity of bare neutral transition metal atoms with alkanes and alkenes. In the 3d series, none of the neutral atoms reacts with alkanes at 300 K, and only Sc, Ti, V, and Ni react with alkenes. Here the authors report state-specific kinetics data for the 4d series. The 4d[sup 10] ([sup 1]S[sub 0]) ground state of the Pd atom reacts rapidly with ethylene, propylene, cyclopropane, and 1-butene and moderately rapidly with ethane, propane, and n-butane at 300 [+-] 5 K in 0.5-0.8 Torr of He. The latter are apparently the first clear-cut examples of gas-phase chemistry between a neutral ground-state transition metal atom and an alkane. Earlier gas-phase studies of Pd reactivity with CH[sub 4] found no reaction of the Pd atom and very slow reaction of the clusters Pd[sub x], x [le] 2. CH[sub 4] is inert to Rh atoms and to Fe atoms. The ground-state Pt atom might react with CH[sub 4], n-hexane, and cyclohexane, but interpretation was complicated by the possible presence of excited-state atoms or of multiphoton ionization and fragmentation. 20 refs., 1 fig., 1 tab.
52 citations
TL;DR: In this paper, a cyclobutane ring was found not to be 100% in the direction of cleavage in a cyclopropane ring of 1,1-disubstituted 2-vinylcyclopropanes.
Abstract: Radical polymerizations of 1,1-disubstituted 2-vinylcyclopropanes CH 2 =CH(C 3 H 3 X 2 ) (X=Cl; X=CO 2 Et; X= CN) was carried out, and the structures of the obtained polymers, mechanism of the polymerization, and volume change on polymerization were studied. From NMR data, a unit which was supposed to have a cyclobutane ring was confirmed in addition to the 1,5-type ring-opened unit. On the basis of the structure of the polymer, the selectivity in the direction of cleavage of the cyclopropane ring of 1a was found not to be 100%. Molecular orbital calculations suggest that the formation of of the cyclobutane unit is thermodynamically possible and the selectivity in the direction of cleavage of the cyclopropane ring of 1a is lower than that of 1b from the difference of two-center energies
51 citations
TL;DR: Treatment of a 7-epi taxol derivative with DAST in dichloromethane led to an unexpected reaction involving participation of the C-19 methyl group and clean formation of a cyclopropane ring as discussed by the authors.
Abstract: Treatment of a 7-epi taxol derivative with DAST in dichloromethane led to an unexpected reaction involving participation of the C-19 methyl group and clean formation of a cyclopropane ring
49 citations
TL;DR: The presence of a carbamate moiety can dramatically alter the outcome of a Heck cyclization, so that the normal exo-cyclization is not followed by β-elimination, but by cyclopropane formation, rearrangement, and elimination.
Abstract: The presence of a carbamate moiety can dramatically alter the outcome of a Heck cyclization, so that the normal exo-cyclization is not followed by β-elimination, but by cyclopropane formation, rearrangement, and elimination
45 citations
TL;DR: In this paper, a new technique is introduced for optimization of valence-bond wave functions; this consists of evaluating energy derivatives with respect to orbital coefficients and applying a steepest descent algorithm.
Abstract: A new technique is introduced for optimization of valence-bond wave functions; this consists of evaluating energy derivatives with respect to orbital coefficients and applying a steepest descent algorithm. Application to cyclopropane predicts a bonding structure of D 3h symmetry with free equivalent C-C bonds. The C-C bonds are localized between each two carbon atoms and are bent with orbital amplitude concentrated outside the ring. The bonding picture in cyclopropane is compared to ethylene, ethane, and diborane
45 citations
TL;DR: The reaction of dimethyldioxirane with several alkynes gives products which are conveniently rationalized by postulating the intermediacy of oxirenes and oxocarbenes.
Abstract: The reaction of dimethyldioxirane with several alkynes gives products which are conveniently rationalized by postulating the intermediacy of oxirenes and oxocarbenes. The latter serve as precursors to H atom or methyl group migration products, as well as to cyclopropane insertion products in some cases. Alkenes, derived from some of these carbene reactions, are partially converted to epoxides
TL;DR: In the presence of a palladium(0) catalyst, ketone α-carbonates react with norbornene to give a cyclopropane derivative via an oxa-π-allylpalladium intermediate as discussed by the authors.
Abstract: In the presence of a palladium(0) catalyst, ketone α-carbonates react with norbornene to give a cyclopropane derivative via an oxa-π-allylpalladium intermediate
TL;DR: Fluoroalkyl-substituted bicyclic and tricyclic olefins were polymerized by ring-opening olefin metathesis polymerization (ROMP) as discussed by the authors.
Abstract: Fluoroalkyl-substituted bicyclic and tricyclic olefins were polymerized by ring-opening olefin metathesis polymerization (ROMP). The monomers used were mixtures of exo- and endo-isomers of 5,5,6-trifluoro-6-(trifluoromethyl)spiro(bicyclo[2.2.1]hept-2-ene-7,1'-cyclopropane), 5,6-difluoro-5(trifluoromethyl)-6-(heptafluoroisopropyl)bicyclo[2.2.1]hept-2-ene, and 2,9,9,4,4,5,5,6-fluorotricyclo[2.2.1]hept-2-ene obtained by the Diels-Alder reaction of cyclopentadiene and spiro[2.4]hepta-4,6-diene with perfluorinated olefins
TL;DR: In this article, single electron transfer induced elemental steps have been shown to occur during the transformation of iodomalonic esters and related CH-acids to cyclopropane derivatives under solid-liquid phase transfer catalytic conditions.
TL;DR: The Michael addition of optically active 3, 4-diphenyloxazolidinone 5 to 2-chloro-2-cyclopropylideneacetates yields 2′-substituted 2-oxo-3, 4D-oxozolidin-3-yl)acetates 6-R with excellent trans-selectivity, which upon reductive dehalogenation and subsequent hydrogenolysis give free 2-(1′-amino-cyclopropyl)acetic acids 9.
TL;DR: In this paper, a mechanistic explanation for the stereoselectivity of cyclopropane derivatives was given, and the yields of the reaction products were substantially improved by using a catalyst (Aliquat 336 or TPBP) under phase transfer conditions.
TL;DR: Perfluoroalkylmethyl-substituted electrophilic cyclopropane derivatives are readily synthesized in excellent yields by a CrCl 3 /Fe promoted reaction of perfluoroalkymyl iodides with allylmalonate and its analogues in one-pot reaction as mentioned in this paper.
TL;DR: In this paper, the conversion of functionalised cyclopropane compounds to derivatives of cyclopentane and five-membered heterocycles is described, including reaction conditions, the regio-and stereo-selectivity of the reactions depending on the type of substituents in the threemembered ring.
Abstract: The conversion of functionalised cyclopropane compounds to derivatives of cyclopentane and five-membered heterocycles is described. Topics discussed include reaction conditions, the regio- and stereo-selectivity of the reactions depending on the type of substituents in the three-membered ring, and also the main procedures for obtaining appropriate cyclopropane substrates. The bibliography includes 174 references.
TL;DR: The synthesis and polymerization chemistry of 1,1-bis(XCH 2 )cyclopropane was studied in this article, and a general method for alkylating norbornadiene in the 2-position was developed.
Abstract: The synthesis and polymerization chemistry of 1,1-bis(XCH 2 )cyclopropane {1, X=OH; 4, X=I} was studied. Treatment of 1 with base in the presence of α,ω-dihalides did not produce a polyether. However, treatment of 4 with the bis(alkoxide) derived from heranediol afforded a polyether of low molecular weight {M n =3000, PD=3}. A general method for alkylating norbornadiene in the 2-position was developed. Treatment of norbornadiene with tert-BuOK, tetramethylethylenediamine (TMEDA), n-BuLi, and tributylchlorostannane (in that order) afforded 2-(tributylstannyl)norbornadiene in excellent yield. On the other hand, carbon electrophiles {e.g. bromobutane, 1,4-dibromobutane, and 2,3-dichloropropene} required the generation of the 2-(lithiocyanocuprate) in order to effect clean alkylation. Treatement of 2-[3-(2-chloropropenyl)]norbornadiene (8a) with RMgX {where R=vinyl and phenyl} in the presence of (dppp)NiCl 2 afforded the cross-coupling products 2-(XCH 2 )-norbornadiene {9,X=2-buta-1,3-dienyl; 10,X=α-styryl; respectively} in high yield. Polymerization of 9 in THF initiated by buli resulted in an elastomeric polymer (12) [M n =18,000, PD=1.5]. Photolysis of 12 in the presence of (Ph 3 P) 2 CuBr converted the pendant norbornadiene to quadricyclane . Heating of the photoisomerized sample to 180°C caused an exothermic (by DSC) reaction which corresponded to 59% of theory
TL;DR: In this article, the reaction of functionalized oxiranes with the sulfur- or silicon-stabilized anions provides β-heteroatom-substituted γ,δ-unsaturated epoxides with, for 5e,f, a trans C=C moiety.
Abstract: The reaction of functionalized oxiranes 1 with the sulfur- or silicon-stabilized anions 2 provides β-heteroatom-substituted γ,δ-unsaturated epoxides 5 with, for 5e,f, a trans C=C moiety. A cis compound 9 is obtained using acetylide anion 2c via 7 and subsequent partial hydrogenation of the C≡C bond in the intermediate oxirane 8. Regiospecific anion generation in 5,9is achieved by deprotonation, reductive desulfurization, and desilylation, respectively.The resulting anions 10 cyclize to 1-(hydroxyalkyl)-2-vinylcyclopropanes 11 by a stereochemically controlled S N i process.Starting from the optically active epoxide 1b,the approach allows synthesis of cyclopropane 11b with (1S,2R) configuration at the ring carbon atoms.This compound can be further elaborated to be algae sex pheromone dictyopterene A which is obtained along with the unnatural Z diastereomer
TL;DR: The Metalla Claisen reaction followed by a 1,3-elimination generates a diastereoselectively substituted metallated cyclopropane as discussed by the authors, which can be used to produce cyclopropellant.
TL;DR: In this paper, a two-dimensional long-range 13C1H J-resolution spectroscopy (LRCJR) was used to measure three-bond 13C 1H coupling constants [3J(C,H)] for trans- and cis-chrysanthemic acid, methyl trans-pyrethrate and some microsomal metabolites of the trans-chryanthemate biophenothrin.
Abstract: Two-dimensional long-range 13C1H J-resolution spectroscopy (LRCJR) was used to measure three-bond 13C1H coupling constants [3J(C,H)] for trans- and cis-chrysanthemic acid, methyl trans-pyrethrate and some microsomal metabolites of the trans-chrysanthemate biophenothrin. The carbon of the methyl cis-disposed to an attached proton shows a larger 3J(C,H) value than does the trans-carbon for the dimethyl-substituted cyclopropane and epoxide rings. The reverse situation applies for the analogous dimethyl vinyl grouping. The 3J(C,H) values are not altered on conversion of one of the olefinic geminal methyl groups to a hydroxymethyl or methoxycarbonyl functionality, but increase on transformation to an aldehyde. These 3J(C,H) values are in agreement previous results from long-range CH COSY experiments, and provide a useful method for determining the stereochemistry of chrysanthemic acid derivatives.
TL;DR: The cyclisation of α-cyano-α-sulphonyl-γ,γ,δ-epoxy carbanions proceeds with high yields and complete diastereoselectivity, to yield cyclopropanolactones, useful intermediates in the synthesis of cis-substituted cyclopricane carboxylic acids as discussed by the authors.
TL;DR: In this paper, it was shown that cyclopropane ring opening with cleavage of the C(1)-C(n+2) (ring enlargement) or C( 1)-C (n+3) bonds can be achieved with triethylamine and lithium perchlorate (LiClO4) in the presence of substituted bicyclo[n.1.0]alkan-2-ones.
TL;DR: The deep-water New Caledonian sponge Cladocroce incurvata contains two «polyketide» metabolites which appear to be derived from fatty acids with ethyl side chains, thus incorporating butyrate units.
Abstract: The deep-water New Caledonian sponge Cladocroce incurvata contains two «polyketide» metabolites. Cladocrocin A {1} appears to be derived from fatty acids with ethyl side chains, thus incorporating butyrate units. Cladoctoic acid {2} is a straight chain fatty acid which incorporates a terminal enyne functionality and a cyclopropane ring directly attached to the carboxylic acid function. The structures were elucidated by interpretation of spectral data, and the cis stereochemistry of the cyclopropane ring in cladocroic acid {2} was derived after the synthesis of cis- and trans-2,3-methanohexanoic acid models and nmr spectral comparisons
TL;DR: In this paper, a reaction of C60 with an equimolar amount of chlorophenyldiazirine in refluxing toluene afforded the C60-chlorophenylcarbene 1:1 adduct in 37% yield.
Abstract: A reaction of C60 with an equimolar amount of chlorophenyldiazirine in refluxing toluene afforded the C60-chlorophenylcarbene 1:1 adduct in 37% yield. The adduct was shown to have the cyclopropane structure by 13C NMR and exhibited reversible reduction waves at the potential about 0.1 V more negative and an irreversible oxidation peak at nearly the same potential as compared with those of C60 itself.
TL;DR: In this article, the direct synthesis of dihydrofurans from α-diazoketones with metal catalysts in the presence of ethyl vinyl ether rearranged spontaneously.